Answer:
Fort Duquesne was located at the site of a former British fort which was taken in 1754 before the French and Indian war. The French officers decided to destroy it but, judging its eminently strategic position, they erected a new one. The most important of these posts was that it was constructed at the confluence of the Monongahela and Allegheny rivers, to the point where their united waters form the Ohio. This fort was projected on the model of Fort Frontenac: it was a bastioned square, a little smaller than the first, a plan generally adopted for all the fortifications of the same destination in America.